The
the family 3 of glycoside hydrolase gathers near 5000 enzymes of fungal, bacterial and plant origin. These enzymes show a broad range of enzymatic specificities
such as β-glucosidase, xylan 1,4-β-xylosidase, β-N-acetylhexosaminidase, glucan 1,3-β-glucosidase, glucan 1,4-β-glucosidase, exo-β-1,3-β-1,4-glucanase,
α-L-arabinofuranosidase and chitosanase.

So far (oct. 2013), the only known chitosanases belonging to GH3 family were produced by the cyanobacteria Anabaena fertilissima and Anabaena sphaerica.
Studies by Gupta et al. (120, 121) revealed for the first time that the antifungal activities secreted by of these cyanobacteria
were correlated with the production of chitosanases. The purified chitosanase from Anabaena fertilissima acted by an endo-type mechanism.